Before: A deep brunette shade with lighter brown highlights. Very dark hair can look inky and dull, so if you're going dark, ask your colorist for a "multitonal chocolate with caramel ribbons running from midlength to the ends," says hairstylist George Papanikolas of Andy LeCompte Salon in Los Angeles.

After: Honey blonde can go oh so wrong with olive skin. That's why Papanikolas, who lightened Kardashian's hair, kept depth close to her head so she didn't look washed out. "The key is painting fine highlights at the roots that gradually get thicker and heavier towards midlength and the ends," he says.

Before: At the punk-themed Met Gala, Hathaway gave a solid middle finger to the notion that you should stay within two shades of your natural hair color by showing up Debbie Harry platinum. "I've wanted to do it forever," Hathaway told Allure correspondent Jeffrey Slonim on the red carpet. "I have to turn it back for work, but this might become a thing." light."

After: Just three weeks later, Hathaway was back to her trademark brunette. "The dark brown is closer to her natural hair color and is much more flattering," Papanikolas says. To re-create it, ask your colorist for tone-on-tone color—a rich chocolate brown base and darker lowlights. "Then do a gloss that's one to two shades lighter," he says. "The subtle difference makes hair look multidimensional and reflects

Before: Reprising her role as Katniss Everdeen in The Hunger Games: Catching Fire sent Lawrence to the dark side. "The rich chestnut here is a tone that occurs when someone starts off dark brown and lets it fade a bit," says Avon Global Hair Color Expert Lorri Goddard. "You always get a little bit of warmth coming through."

After: This sun-kissed blonde is downright gorgeous on Lawrence. Not a surprise, since her natural color—"dark blonde with little streaks of light brown in the back," says Goddard, who lightened her hair—is a close match. "We used that for her base color," she says. "Then I wove in a mixture of wide and thin sections of brightness. It has to be imperfectly perfect, just as it would occur in nature." Ask your colorist for subtle highlights near the scalp and thicker ribbons from midlength to the ends, so growing it out isn't a hassle.

Before: Moretz, a blonde by birth, made the transition to moody brunette with this rich auburn color with "superfine highlights barely glimmering around the face," says Goddard, who gave her the makeover. "For brunettes, it's imperative to layer in textures like lowlights or tiny strands of light just around the face so that the color doesn't look flat."."

After: "We put a lot of colors in there to get this surfer-girl hair," Goddard says of the multidimensional blonde she created for Moretz. To complement her natural blonde color at the roots, Goddard wove in shades of caramel, honey, and baby blonde. "Then I went lighter towards the bottom," she says. "It's what happens in nature if someone is out on the surfboard with a ponytail and the sun lightens the hair

Before: Rihanna has rocked bright blonde and Ronald McDonald red in the past, but these pretty ginger waves—they almost look like they belong on Lindsay Lohan's head—took everyone by surprise. "The look is beached-out Little Mermaid meets rock and roll princess," says Goddard. Red hair dye fades the fastest, so be sure to use a color-preserving shampoo and conditioner, otherwise hair gets less auburn and more copper with every wash.

Before: Wilde spent the beginning of her career as a beachy blonde (remember The O.C.?), but that doesn't mean every blonde is one size fits all. This sandy color "is too close to her skin tone," says Papanikolas.

After: No mousy browns here. "The graduation of color and beachy highlights keeps it fresh," says Papanikolas. "Ask your colorist for balayage if you want to get that delicate transition from dark to light without looking dip-dyed."

Before: Jessie J has tried more colors over the past two years than many of us will in a lifetime—brown, purple, black with blonde dip-dye—but this geometric, jet black bob has become her signature. The vinyl shine is what makes it spectacular; get it with a glossing treatment like Fekkai Salon Glaze Clear Shine Rinse between color appointments.

After: In March, she shaved her head live on TV to raise money for British charity Comic Relief. Then she decided to see if blondes had more fun, tweeting a selfie of her newly grown-in, freshly bleached coif. "Her Alfred Hitchcock blonde brings focus and light to her eyes and brightens her skin," says Goddard. If you have dark or colored hair and want to go blonde, make sure your colorist bleaches it in stages—no more than two shades per appointment—so you don't fry it.

Before: We were always feeling her medium blonde incarnations, but in icy platinum, Mulligan took her Mia Farrow crop to the next level. One reason it works so seamlessly: Her brows were lightened to help the pale color harmonize with her skin tone.

After: Peroxide can be stunning—and punishing. Case in point: Mulligan gave the bleach a break and became a brunette. Remember that when going from blonde to brown, hair needs to be healthy, moisturized, and freshly trimmed to ensure evenly absorbed color from roots to tips.

Before: The Insidious actress is known for her eye-catching brown hair. (Her secret: a color laced with threads of gold.) Going dark? If your natural hair color is light, ask for a golden brown base; if it's dark, ask for ash brown.